您也可以使用Graphics32库或者我之前从CodeCentral中抓取的这个函数:
procedure SmoothRotate(var aPng: TPNGImage; Angle: Extended);
function TrimInt(i, Min, Max: Integer): Integer;
begin
if i>Max then Result:=Max
else if i<Min then Result:=Min
else Result:=i;
end;
function IntToByte(i:Integer):Byte;
begin
if i>255 then Result:=255
else if i<0 then Result:=0
else Result:=i;
end;
function Min(A, B: Double): Double;
begin
if A < B then Result := A else Result := B;
end;
function Max(A, B: Double): Double;
begin
if A > B then Result := A else Result := B;
end;
function Ceil(A: Double): Integer;
begin
Result := Integer(Trunc(A));
if Frac(A) > 0 then
Inc(Result);
end;
function newsize: tsize;
var
fRadians: Extended;
fCosine, fSine: Double;
fPoint1x, fPoint1y, fPoint2x, fPoint2y, fPoint3x, fPoint3y: Double;
fMinx, fMiny, fMaxx, fMaxy: Double;
begin
fRadians := (2 * PI * Angle) / 360;
fCosine := abs(cos(fRadians));
fSine := abs(sin(fRadians));
fPoint1x := (-apng.Height * fSine);
fPoint1y := (apng.Height * fCosine);
fPoint2x := (apng.Width * fCosine - apng.Height * fSine);
fPoint2y := (apng.Height * fCosine + apng.Width * fSine);
fPoint3x := (apng.Width * fCosine);
fPoint3y := (apng.Width * fSine);
fMinx := min(0,min(fPoint1x,min(fPoint2x,fPoint3x)));
fMiny := min(0,min(fPoint1y,min(fPoint2y,fPoint3y)));
fMaxx := max(fPoint1x,max(fPoint2x,fPoint3x));
fMaxy := max(fPoint1y,max(fPoint2y,fPoint3y));
Result.cx := ceil(fMaxx-fMinx);
Result.cy := ceil(fMaxy-fMiny);
end;
type
TFColor = record b,g,r:Byte end;
var
Top, Bottom, Left, Right, eww,nsw, fx,fy, wx,wy: Extended;
cAngle, sAngle: Double;
xDiff, yDiff, ifx,ify, px,py, ix,iy, x,y, cx, cy: Integer;
nw,ne, sw,se: TFColor;
anw,ane, asw,ase: Byte;
P1,P2,P3:Pbytearray;
A1,A2,A3: pbytearray;
dst: TPNGImage;
IsAlpha: Boolean;
new_colortype: Integer;
begin
if not (apng.Header.ColorType in [COLOR_RGBALPHA, COLOR_RGB]) then
raise Exception.Create('Only COLOR_RGBALPHA and COLOR_RGB formats' +
' are supported');
IsAlpha := apng.Header.ColorType in [COLOR_RGBALPHA];
if IsAlpha then new_colortype := COLOR_RGBALPHA else
new_colortype := COLOR_RGB;
dst := tpngobject.Create;
with newsize do
dst.createblank(new_colortype, 8, cx, cy);
cx := dst.width div 2; cy := dst.height div 2;
Angle:=angle;
Angle:=-Angle*Pi/180;
sAngle:=Sin(Angle);
cAngle:=Cos(Angle);
xDiff:=(Dst.Width-apng.Width)div 2;
yDiff:=(Dst.Height-apng.Height)div 2;
for y:=0 to Dst.Height-1 do
begin
P3:=Dst.scanline[y];
if IsAlpha then A3 := Dst.AlphaScanline[y];
py:=2*(y-cy)+1;
for x:=0 to Dst.Width-1 do
begin
px:=2*(x-cx)+1;
fx:=(((px*cAngle-py*sAngle)-1)/ 2+cx)-xDiff;
fy:=(((px*sAngle+py*cAngle)-1)/ 2+cy)-yDiff;
ifx:=Round(fx);
ify:=Round(fy);
if(ifx>-1)and(ifx<apng.Width)and(ify>-1)and(ify<apng.Height)then
begin
eww:=fx-ifx;
nsw:=fy-ify;
iy:=TrimInt(ify+1,0,apng.Height-1);
ix:=TrimInt(ifx+1,0,apng.Width-1);
P1:=apng.scanline[ify];
P2:=apng.scanline[iy];
if IsAlpha then A1 := apng.alphascanline[ify];
if IsAlpha then A2 := apng.alphascanline[iy];
nw.r:=P1[ifx*3];
nw.g:=P1[ifx*3+1];
nw.b:=P1[ifx*3+2];
if IsAlpha then anw:=A1[ifx];
ne.r:=P1[ix*3];
ne.g:=P1[ix*3+1];
ne.b:=P1[ix*3+2];
if IsAlpha then ane:=A1[ix];
sw.r:=P2[ifx*3];
sw.g:=P2[ifx*3+1];
sw.b:=P2[ifx*3+2];
if IsAlpha then asw:=A2[ifx];
se.r:=P2[ix*3];
se.g:=P2[ix*3+1];
se.b:=P2[ix*3+2];
if IsAlpha then ase:=A2[ix];
Top:=nw.b+eww*(ne.b-nw.b);
Bottom:=sw.b+eww*(se.b-sw.b);
P3[x*3+2]:=IntToByte(Round(Top+nsw*(Bottom-Top)));
Top:=nw.g+eww*(ne.g-nw.g);
Bottom:=sw.g+eww*(se.g-sw.g);
P3[x*3+1]:=IntToByte(Round(Top+nsw*(Bottom-Top)));
Top:=nw.r+eww*(ne.r-nw.r);
Bottom:=sw.r+eww*(se.r-sw.r);
P3[x*3]:=IntToByte(Round(Top+nsw*(Bottom-Top)));
if IsAlpha then
begin
Top:=anw+eww*(ane-anw);
Bottom:=asw+eww*(ase-asw);
A3[x]:=IntToByte(Round(Top+nsw*(Bottom-Top)));
end;
end;
end;
end;
apng.assign(dst);
dst.free;
end;